Which free body diagram best represents the forces on the mower?

1. Mary pulls on a lawnmower parallel to the surface so that it moves at a constant speed up the hill. y x y x y x y x Which free body diagram best represents the forces on the mower? Construct an FBD that best represents the motion of the mower. 1 2 3 4

2. 400 y 400 x y y 400 x x y 400 x Stacey pulls a mower at 40-degrees relative to the ground. Which free body diagram best represents the forces on the mower? Construct an FBD that best represents the above situation. 1 2 4 3

3. Marsha pulls a sled on ice (no friction) with a 150-N force at an angle of 200. The mass of the sled and her brother is 45 kg. g = 10 m/s2. Stacey represented this situation pictorially and mathematically. x x: (150 N) = (45 kg) ax y: N – (45 kg)(10 m/s2) = (45 kg) 0 Did the student mislabel or forget to include anything? 4 (1) and (3) are needed corrections. 5 (2) and (3) are needed corrections. 6 The above mathematical representation is correct. 1 (150 N) should be (150 N) sin 20o. 2 (150 N) should be (150 N) cos 20o. 3 Include a (150 N) sin 20o term in the y equation.

4. Steve pulls a sled on ice (no friction) with a 150-N force at an angle of 200. The mass of the sled and her brother is 45 kg. g = 10 m/s2. Stacey represented this pictorially and mathematically. o x x: (150 N) cos 20o = (45 kg) ax y: __ N __ (45 kg)(10 m/s2) __ (150 N) sin 20o = 0 What are the missing signs? 1 + – + 2 + + – 3 – – + 4 – – – 5 + + +

5. The motion of a car is represented with the motion diagram below. x y 1 y y 2 3 x x x y 4 y 5 x x o Which diagram best represents the forces exerted on the car by the Earth and the Earth’s surface? Construct a diagram that best represents the forces exerted on the car by the Earth and the Earth’s surface.

6. x: 0 – 0.80 N = (1000 kg)ax y: N – (1000 kg)(10 m/s2) = (1000 kg) 0 0 – 16 m/s = ax t Which word description below best matches the above mathematical description? Construct a verbal description that best matches the above mathematical description. • The 0.80 N force of the Earth on the object causes its speed in the x direction to increase from 0 to 16 m/s. • The object slows down due to a 0.80 N frictional force. • The object has a 10 m/s2 acceleration in the y direction. • The net force causing the object to slow down is exerted in the same direction as the initial velocity. • 5 The object’s velocity increases from 0 to 16 m/s.

7. y 1 y y 2 3 x x x y 4 x Which FBD best represents the above motion diagram for a car? Construct an FBD that best represents the above motion diagram for a car.

8. Which motion diagram best represents the situation shown in the free-body diagram? Construct a motion diagram that best represents the situation shown in the free-body diagram above. 2 1 4 3 5 Either 2 or 4 are possible

9. Which FBD below best represents the forces exerted on the ball as it is moving UP (ignore air resistance)? Construct an FBD that best represents the forces exerted on the ball as it is moving UP. 2 1 3 4

10. Which FBD below best represents the forces exerted on the ball as it is moving DOWN (ignore air resistance)? Construct an FBD that best represents the forces exerted on the ball as it is moving DOWN. 2 1 3 4

11. Which FBD below best represents the forces exerted on the ball at the TOP of its path? Construct an FBD that best represents the forces exerted on the ball at the TOP of its path. 2 1 4 3 5 No forces are exerted on the ball

12. y x Construct a motion diagram that best represents the situation shown in the free-body diagram above. Which motion diagram best represents the situation as shown by the free-body diagram? 2 1 4 3 5 No diagram -- the stroller must be accelerating to the right because the net force is to the right.

13. y x Which speed versus time chart best represents this situation? Construct a speed versus time chart that best represents this situation. 1 3 v v v t t t